As is known in the book panel and bookbinding industry, hardcover books 10 generally have a solid front panel 20 and a solid rear panel 21 with a flexible middle binding section 25 as shown in FIG. 1.
The front and rear panel portions 20 and 21 typically are formed of a multi-layered solid laminated chipboard as shown in the prior art drawing of FIG. 2B.
The laminated solid chipboard structures of the prior art typically comprise five or more layers, three of which are shown at 31, 32 and 33 of FIG. 2B. Each layer must be fully joined to an adjacent layer by adhesives 35 as is known in the art.
Chipboard is a term known to those of skill in the art to signify paper products processed from, for example, waste paper materials and thus having relatively short fiber lengths contained therein as shown at numerals 40 in the prior art showing at FIG. 2B.
Because chipboard is, by definition, formed of short fiber length materials, it inherently has low original position memory. That is, once bent, chipboard is unable to successfully return to its original desired flat position. Because of such low memory by chipboard products, it has been required to utilize five or more chipboard layers in the formation of a book panel. The required usage of such a high number of chipboard layers has increased adhesives costs and manufacturing time and materials costs generally.
Accordingly, it is an object of the present invention to provide a book panel structure which is less costly to manufacture and ship than the conventionally used laminated solid chipboard design.
It is a further object to reduce manufacturing costs by effectively using air cells within the book panel assembly to reduce overall materials costs.
It is a still further object of the invention to significantly reduce the cost of adhesives used in the production of book panels.
It is a further object to demonstrate a book panel construction which can be bent without the cracking inherent in prior art designs.
It is a still further object to provide a book panel construction which has a higher original position memory than has been heretofore known in the art.
It is a further significant object of the present invention to produce a book panel having the same or increased thickness as prior art designs while decreasing panel weight and improving panel durability.
It is also an object of the invention to demonstrate an advantageous book panel construction which utilizes an undulated midstratum layer having significantly longer average fiber lengths relative to an overlayer and underlayer which are formed of chipboard materials having significantly shorter average fiber lengths therein.
Further objects and advantages of the present invention will become apparent as the following description proceeds, and the features of novelty characterizing the invention will be pointed out with particularity.